This invention relates to a chromium carbide sintered body. More particularly, it relates to a highly tough chromium carbide sintered body having superior corrosion resistance to molten metal or components of industrial furnaces, such as heating furnaces.
A chromium carbide sintered body has been produced with addition of various sintering aids to chromium carbide. The sintering aids so far proposed include powders of metals, such as Co, Fe, Ni or Ni-P alloys, borides such as titanium boride or zirconium boride, carbides such as tantalum carbide, boron carbide or silicon carbide, oxides such as aluminum oxide, chromium oxide or magnesium oxide, phosphides such as iron phosphide, cobalt phosphide or chromium phosphide, and nitrides such as chromium nitride, titanium nitride or aluminum nitride. These sintering aids are used in amounts of not more than 10 wt. % based on the weight of chromium carbide, and the sintering temperature is set so as not to be higher than 1500.degree. C. (see Japanese Laid-open Patent Publication No. 107972/1984). However, the sintered body containing acicular crystals of chromium carbide cannot be obtained by this prior art technique. Concerning the structure of the chromium carbide sintered body, although coarse-sized or granular crystals have been reported, examples of formation or utilization of the needle-shaped or columnar crystals have not been found (see for example "Some Properties of Chromium Carbide Ceramic Material", Nippon Tungsten Review, Vol. 19 (1986))
Although a chromium carbide type ceramic material is known to have excellent anti-oxidation and anti-scaling properties, it has been reported that such material is not fully satisfactory in strength, hardness, fracture toughness and thermal impact resistance. Hence, the situation is that the usage of the material is restricted to skid rails or skid buttons in heating furnaces.
The fiber reinforcing method has also been practiced for improving mechanical or thermal impact resistance which represents in general the most vulnerable points of the ceramic material. This method consists in uniformly dispersing whiskers having lengths of several tens to hundreds of microns or fibers of longer lengths into the interior of the sintered body. Although some effects may be realized by this method, it cannot be said that the method has gained widespread acceptance on account of elevated costs caused by the use of whiskers and difficulties in uniformly dispersing the whiskers or fibers.